Heartworms can cause severe and possibly fatal illness in dogs, cats and ferrets year-round in all 50 states, even if they spend all their time indoors, according to the FDA. Prevention is key, as no medication is approved to kill adult heartworms in cats or ferrets, and killing adult heartworms in dogs requires a dangerous arsenic-based medication, but prevention is easy with year-round preventive pills, injections or topical medications, the FDA says.
